Multimodulation transmitter

• US 20050215206A1
• Filed: 03/19/2003
• Published: 09/29/2005
• Est. Priority Date: 04/05/2002
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Granstrom, Anders, Johansson, Gunnar
• Granted Patent: US 7,469,017 B2
• Time in Patent Office: Days
• US Class Current: 455/102
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths

Abstract

The present invention discloses a double TRU (Transceiver Unit) (45). The output signals from the power amplifiers (64, 84) are combined to one common output signal provided to an antenna arrangement (91). A DSP (Digital Signal Processor) (52, 72) of each TRU (50, 70) comprises means for a constant-envelope modulation scheme (54, 74) and a non-constant envelope scheme (53, 73). The DSP:s (52, 72) select the modulation scheme according to modulation information (49, 69). In such a way, a switching between different modulation schemes can be performed even on a time-slot basis. For non-constant-envelope modulation, the modulated signal is separated into two component signals. Each TRU (50, 70) takes care of the amplification of one component. A phase compensation of at least one of the TRU:s (50, 70) is performed in order to correct for different paths of phases of the power amplifiers (64, 84). The non-constant envelope modulated signal can also be a multi-carrier signal, e.g. of two or more constant-envelope signals. Also a TCC (Transmitter Coherent Combining) operation is achievable.

Claims

1. Transmitter arrangement, comprising:

a first modulation unit having a first digital signal processor and a first analogue signal generator;

said first digital signal processor having a first digital signal input;

a first power amplifier, connected to an output of said first analogue signal generator;

a second modulation unit having a second digital signal processor and a second analogue signal generator;

said second digital signal processor having a second digital signal input;

a second power amplifier, connected to an output of said second analogue signal generator;

combiner device connected to outputs of said first and second power amplifiers; and

transmitter device connected to an output of said combiner device, said first digital signal processor further comprises

at least one first non-constant envelope modulation means;

a first signal component separator connected to an output of said at least one first non-constant envelope modulation means;

a first output of said first signal component separator being connectable to said first analogue signal generator;

first means for receiving modulation instructions;

at least one first constant envelope modulation means connectable to said first analogue signal generator;

and first modulation selecting means for connecting a modulation means to said first digital signal input in response to received modulation instructions.

2. Transmitter arrangement according to claim 1, wherein said second digital signal processor further comprises:

at least one second non-constant envelope modulation means of the same type as said at least one first non-constant envelope modulation means; and

a second signal component separator connected to an output of said at least one second non-constant envelope modulation means;

an output of said second signal component separator being connectable to said second analogue signal generator;

a sum of a signal of said first output of said first signal component separator and a signal of said output of said second signal component separator being equal to a signal of said output of said at least one first non-constant envelope modulation means.

3. Transmitter arrangement according to claim 1, wherein a second output of said first signal component separator being connectable to said second analogue signal generator.

4. Transmitter arrangement according to claim 1, wherein said second digital signal processor further comprises:

second means for receiving modulation instructions;

at least one second constant envelope modulation means connectable to said second analogue signal generators; and

second modulation selecting means for connecting a modulation means to said second digital signal input in response to received modulation instructions.

5. Transmitter arrangement according to claim 4, wherein said first and second modulation selecting means are operable on a time slot basis.

6. Transmitter arrangement according to claim 1, further comprising:

first power monitor sensing a total power to said transmitter device or a quantity directly related thereto; and

phase-shifter connected to said first power monitor, arranged for causing a phase shift of an analogue signal generated by said first analogue signal generator in response to said sensed total power.

7. Transmitter arrangement according to claim 6, wherein said first power monitor is a power meter of a load of said combiner device.

8. Transmitter arrangement according to claim 6, wherein said phase-shifter comprises means for complex multiplication of said phase shift with a digital signal to be inputted to said analogue signal generator.

9. Transmitter arrangement according to claim 6, using GMSK modulation, wherein said phase-shifter comprises means for introducing a phase offset in said GMSK modulation, generated by using a table driven state machine in said first digital signal processor.

10. Transmitter arrangement according to claim 6, further comprising means for providing said first and second digital inputs with the same digital signal, and said first and second means for receiving instructions with the same instructions of a constant envelope modulation, allowing transmitter coherent combining.

11. Transmitter arrangement according to claim 6, further comprising:

second power monitor sensing a power on said output of said first power amplifier and being connected to said phase-shifter; and

third power monitor sensing a power on said output of said second power amplifier and being connected to said phase-shifter;

said phase-shifter being arranged for causing a phase shift in response to a comparison between said sensed total power and said sensed power on said output of said first and second power amplifier, respectively.

12. Transmitter arrangement according to claim 1, wherein that said first and second non-constant envelope modulation means are selected from the list of:

4-PSK modulation means;

8-PSK modulation means; and

means for combination of at least two carriers.

13. Transmitter arrangement according to claim 4, wherein said first and second constant envelope modulation means are GMSK modulation means.

14. Method for generating a transmitter signal in a transmitter arrangement having at least a first and a second modulation unit arranged in parallel, each one allowing for at least one non-constant envelope modulation and at least one constant envelope modulation, said first modulation unit having a first analogue signal generator, said second modulation unit having a second analogue signal generator, comprising the steps of:

providing digital signal to said first and second modulation units;

providing modulation information to said first and second modulation units;

creating a first input signal to said first analogue signal generator by performing a constant envelope modulation of a first digital signal provided to said first modulation unit as a response of said modulation information being a request for a constant envelope modulation, and by performing a non-constant envelope modulation of said first digital signal and separating a first component of said non-constant envelope modulated first digital signal as a response of said modulation information being a request for a non-constant envelope modulation;

creating a second input signal to said second analogue signal generator by performing a constant envelope modulation of a second digital signal provided to said second modulation unit as a response of said modulation information being a request for a constant envelope modulation, and by performing a non-constant envelope modulation of said first digital signal and separating a second component of said non-constant envelope modulated first digital signal as a response of said modulation information being a request for a non-constant envelope modulation;

generating a first output signal in said first analogue signal generator according to said first input signal;

generating a second output signal in said second analogue signal generator according to said second input signal;

amplifying said first output signal;

amplifying said second output signal;

combining said first and second amplified output signals to form an analogue transmitter signal.

15. Method according to claim 14, wherein said providing steps are performed on a time slot basis.

16. Method according to claim 14, wherein said modulation information comprises a request for a non-constant envelope modulation, whereby said step of creating a second input signal to said second analogue signal generator is performed on said first signal in said first modulation unit, said method comprising the further step of transferring of said second input signal from said first modulation unit to said second analogue signal generator.

17. Method according to claim 14, characterized in wherein said modulation information comprises a request for a non-constant envelope modulation, and said second digital signal is identical with said first digital signal, whereby said step of creating a second input signal to said second analogue signal generator is performed on said second signal in said second modulation unit.

18. Method according to claim 16, wherein said non-constant envelope modulation is a 8-PSK modulation.

19. Method according to claim 16, characterized in that said non-constant envelope modulation is a multiple-carrier GMSK modulation, whereby said method comprises the steps of providing a set of at least two digital signals to both said first and said second modulating units, whereby said creating steps comprise the steps of performing a GMSK modulation of each digital signal and digital combining said modulated signals to form a non-constant envelope multi-carrier signal, whereby said separating step is performed on said non-constant envelope multi-carrier signal.

20. Method according to claim 14, wherein said modulation information comprises a request for transmitter coherent combining of a constant envelope modulation signal, and said first digital signal is identical with said second digital signal.

21. Method according to claim 16, comprising the further steps of:

monitoring a power of said analogue transmitter signal or a quantity directly related thereto; and

shifting a phase of said first output signal according to said power.

22. Method according to claim 21, wherein said monitoring step comprises the step of measuring a power rejected during said combining step, whereby said power of said analogue transmitter signal is provided as a complementary quantity.

23. Method according to claim 21, wherein said shifting step in turn comprises the step of adjusting an initial offset phase of said first or second modulating in a guard period between two time slots.

24. Method according to claim 21, wherein said shifting step in turn comprises the step of adding a phase shift in connection to the generation of the first output signal.

25. Method according to claim 16, wherein said monitoring and phase shifting is performed when a constant envelope modulation with transmitter coherent combining is used, whereby said phase shifting is preserved when selecting a non-constant envelope modulation.

26. Method according to claim 16, wherein said monitoring and phase shifting is performed during transmission of a constant amplitude period of a non-constant envelope signal.

27. Method according to claim 16, comprising the further step of measuring instantaneous power of said first and second analogue output signals, whereby said shifting is performed according to a comparison of said power of said analogue transmitter signal and said power of said first and second analogue output signals.

28. Method according to claim 27, wherein said shifting in the case of transmitter coherent combining is performed according to:

φ

_shift=cos<sup>−

1</sup>(P_TR|(P_TX1+P_TX2)),

where P_TR is said total power and P_TX1 and P_TX2 are said power of said first and second analogue output signals, respectively.

29. Method according to claim 27, wherein said comparison is performed during a period of a known training sequence in a time slot.

30. Method according to claim 14, comprising the further steps of:

reducing envelopes of said first and second signals when said modulated signal has a low amplitude.

31. Method according to claim 30, wherein said step of reducing envelopes comprises minimizing of power consumption.

32. Method according to claim 14, comprising the further step of:

storing an adjusted phase shift value for each one of a set of used frequencies.

33. Method according to claim 32, comprising the further step of:

storing an adjusted phase shift value for each one of a set of used frequency generators for each of said used frequencies.